Based on information exchange technologies such as instant messaging (IM), a user can initiate an association establishing request to another userinformation exchange. If the other user accepts the request, then an association relationship can be established between the two users. That is, the two users become “friends”. However, it is more possible for users to become friends if they know each other in the real world. People tend to reject or neglect the association establishing request initiated by an unknown user, which makes it difficult to realize information exchange between users unknown to each other.